The Explanation of the Religions (Bayān al-Adyān, 1091-2) is the first surviving Persian encyclopedia of comparative religions completed before the better-known Arabic-language the Book of Sects and Creeds (Kitāb al-Milāl wa al-Niḥal) by Muḥammad b. ʿAbd al-Karīm Aḥmad al-Shahrastānī from 1127-8. Beyond that, it is the earliest surviving source on the travelogue writer and Ismaili philosopher Nāṣir Khusraw (d. 1088), but despite its significance, the work was shrouded in obscurity. Its author Abū al-Maʿālī Muḥammad mentions in his Explanation of the Religions that a copy of the famous, but unfortunately now lost, picture book of the third century public sage and preacher, Mānī (3rd c.), the Arzhang (Parthian: Ārthang) was preserved in the library of Ghazna. In the introductory part of his work the jurist and translator Abū al-Maʿālī Muḥammad gives his detailed, and possibly fabricated, genealogy linking him to one of the leading figures of Balkh, ʿUbayd Allāh Yār Khudāy, and to ʿAlī b. Abī Ṭālib (d. 661). The style of his book is generally not polemical, though it is not without occasional disparaging remarks.